I voted Clown Loaches above, but really mine is another vote for YoYo loaches. I like that they have all the benefits and personality of clown loaches, but stay at a more aquarium friendly size. Loaches in general have a few goofy behaviors. Such as taking anap by laying on thier side in the middle of the gravel. First couple times you see that you will probably reach for your net, only to have them swim away as you swoop in. They will try and wiggle into any crack in the driftwood, upside down sideways whatever. They like sniffing other fish and will follow the scent trail from fish to fish until they find the block of blood worms.
Botia kubotai (Angelique Loach) are another nice species that stays a bit smaller.